Under paragraph 1(a) of Executive Order 10096, the conditions under which this invention was made entitle the Government of the United States, as represented by the Secretary of the Army, to the entire right, title and interest in any patent granted thereon by the United States. This and related patents are available for licensing. Please contact Bea Shahin at 217 373-7234 or Phillip Stewart at 601 634-4113.
The field is that hydraulic engineering needed to guide, regulate, and modify fluid flow. In particular, a preferred embodiment of the present invention assists fish in circumventing an obstruction in a stream.
Water resources development typically includes the construction of dams across rivers to impound and regulate flows for power production, flood control, water supply, irrigation and other economically beneficial uses of water. In many rivers, adult fish typically migrate upstream through the river to spawn and rear in upstream areas. Once young, or juvenile, fish reach a certain size they instinctively migrate downstream to the adult habitat areas in downstream reaches of the river, in lakes, or in the ocean where they mature into adults and complete their life cycle. Juvenile salmon and many other juvenile fishes are spawned in upstream fresh water systems where the early life stages are completed but reach adulthood in downstream areas.
Unfortunately, dams block the migration of fish and thereby interfere with the completion of their natural life cycles. Sustainable water resources development is often facilitated by the use of hydraulic structures to pass these juvenile fish around the dam and other channel obstructions.
Systems and methods for assisting fish in circumventing man-made barriers in streams have been tried for many years, e.g., U.S. Pat. No. 3,338,056, Fingerling Saving System, issued to Roscoe, Aug. 29, 1967, details a complex arrangement of recesses using vertically oriented entrances for permitting the transport of fingerlings around a dam. Quoting from the ""056 patent: xe2x80x9cThe difficulty (of getting fingerlings downstream) arises due to the tendency of the fingerlings to follow flowing currents of water, and ordinarily such flowing currents go through the turbines of the associated power station. The fingerlings suffer high mortality in passing through the turbines . . . xe2x80x9d
A later patent, U.S. Pat. No. 4,437,431, Method and Apparatus of Diversion of Downstream Migrating Anadromous Fish, issued to Koch, Mar. 20, 1984, uses an xe2x80x9cartificial streamxe2x80x9d generated by water jets within the natural stream together with long tubes having funnel-shaped entrances located on the sides of the stream at some distance from the upstream side of the dam. Another solution that offers an xe2x80x9cattractingxe2x80x9d artificial current based on an active source includes a propeller generated current as described in U.S. Pat. No. 6,102,619, Flow Inducer Fish Guide and Method of Using Same, issued to Truebe et al., Aug. 15, 2000. A related technique involving a series of opening and closing valves, fish passing actuators and conduits is detailed in U.S. Pat. No. 6,273,639 B1, Method and Apparatus for Facilitating Migration of Fish Past Dams and Other Barriers in Waterways, issued to Eikrem et al., Aug. 14, 2001.
To comply with government regulations, other solutions have involved configurations of barrier screens and bypass conduits such as that envisioned by U.S. Pat. No. 4,481,904, Fish Conservation Device, issued to Fletcher, Nov. 13, 1984; U.S. Pat. No. 4,526,494, Penstock Fish Diversion System, issued to Eicher, Jul. 2, 1985; and U.S. Pat. No. 4,740,105, issued to Wollander, Apr. 26, 1988. One such screen barrier uses a number of like modules in a ladder arrangement affixed to the bottom of the channel as described in U.S. Pat. No. 4,929,122, Fish Protection System for Dams, issued to Yoas, May 29, 1990. An underwater xe2x80x9cscreen housexe2x80x9d located adjacent a dam is described in U.S. Pat. No. 5,385,428, Water Intake Fish Diversion Apparatus, issued to Taft et al., Jan. 31, 1995. A buoyant screen that may be sunk and raised at appropriate fish migration times is described in U.S. Pat. No. 5,558,462, Flat Plate Fish Screen System, issued to O""Haver, Sep. 24, 1996.
Still other solutions provide for a buoyant arrangement of vertically oriented slats located some distance upstream from a barrier such as described in U.S. Pat. No. 5,263,833, Fish Guiding Assembly and Method Utilizing Same, issued to Robinson et al., Nov. 23, 1993. This arrangement, and others like it, consumes a considerable amount of the surface area immediately upstream from the dam.
Active solutions are also proposed as exemplified in U.S. Pat. No. 5,445,111, Electrified Fish Barriers, issued to Smith, Aug. 29, 1995, describing linear curtain arrays characterized by pulsed driving signals that may use varying voltages. Other active solutions include complex electronic detectors and control systems to alter the operation of a hydroelectric powerhouse in the presence of migrating fish as described in U.S. Pat. No. 6,038,494, Control System for Enhancing Fish Survivability in a Hydroelectric Power Generation Installation, issued to Fisher et al., Mar. 14, 2000.
Fish ladders have been used to help returning anadromous fish get to spawning beds and are also proposed to help the juveniles return to the sea as described in U.S. Pat. No. 6,155,746, Fish Ladder and Its Construction, issued to Peters, Dec. 5, 2000. This details a complex series of basins having vertical inflow and outflow slots for transporting fish around a barrier.
The above solutions involve a configuration that is either much more complex and costly than a preferred embodiment of the present invention, uses much more xe2x80x9cgeographyxe2x80x9d to effect the desired result, uses energy or large quantities of water to effect the desired result, or a combination of these undesirable factors.
Juvenile outmigrating fish instinctively seek passage through the dam when their downstream journey is blocked. For a detailed discussion, refer to U.S. Pat. No. 6,160,759, Method for Determining Probable Response of Aquatic Species to Selected Components of Water Flow Fields, issued to Nestler et al., Dec. 12, 2000, and incorporated herein by reference. In the Columbia River, conventional surface bypass collectors (SBC""s) are a preferred passage design used at dams for passing outmigrating juvenile fish. A conventional SBC employs a water intake plume to attract fish to its entrance. Using conventional engineering concepts, the SBC""s attract and concentrate fish for conveyance around the dam in a manner that helps prevent their entry into turbines or other high-energy hydraulic conditions where they can be injured or killed. An SBC uses an attracting intake plume of sufficient flow magnitude to overcome the attracting flow of competing inflows such as are present at hydroturbines, sluicegates or spillways. Once juvenile fish enter the SBC they are conveyed to a bypass channel where they continue the migration downstream of the dam. Design of the entrance hydraulic conditions used in conventional SBCs does not incorporate knowledge of the behavior of the juvenile fish in natural streams and rivers. As a consequence, the performance of conventional SBCs varies, with some working well and others not. Poor performance most commonly results from uncertainty about the flow conditions required to attract juvenile fish to the entrance of the SBC. A preferred embodiment of the present invention provides a method that employs natural hydraulic cues.
A need, therefore, exists for an optimum method of guiding migrating fish, in particular juvenile fish, to such bypass channels.
A preferred embodiment of the present invention envisions a system simulating at least one natural hydraulic cue to which fish are responsive in water. Migrating fish that respond to the simulated hydraulic cue may circumvent barriers to their downstream migration, such as booms, weirs, dams, hydroelectric powerhouses, and sluice gates.
The simulated natural hydraulic cue elicits an instinctive response of fish to select a portion of a stream having the mean maximum downstream velocity vector, u, and minimum strain rate variables in the downstream direction with respect to at least the depth and the width of the stream, these two variables represented mathematically as                     ∂        u                    ∂        z              ⁢    and    ⁢          xe2x80x83        ⁢                  ∂        u                    ∂        y              ,
respectively. Ideally, these two variables approach zero.
A preferred embodiment of the present invention uses an oven hood surface bypass collector (OH-SBC), with a main portion having at least one slot opening at the bottom and an extension (with the extension adopting the same profile on the top of the OH-SBC as the main portion) that projects upstream from a barrier along which the OH-SBC is positioned. The extension eliminates at least one zone of dead water adjacent the upstream side of the barrier, being positioned facing upstream and the farthest part of the OH-SBC from the barrier. The top of the OH-SBC is generally parallel to the surface of the water, in which it operates and its depth is selected so that passage of fish of a pre-specified size is facilitated.
The basic unit of the OH-SBC, which may consist of multiple units or modules, is structured to circumscribe an internal sluiceway running parallel to the upstream side of the barrier under the wedge-shaped extension and a collection gallery that parallels the sluiceway immediately adjacent to the upstream side of the barrier, the collection gallery being circumscribed by the main portion of the OH-SBC.
Fish are attracted to the collector gallery by the simulated hydraulic cue maintained by the Natural Cue SBC (NC-SBC) system, and are moved around the barrier by de-watering the collector gallery. An articulating extension may be affixed to the lower part of the collection gallery to control the xe2x80x9cangle of attackxe2x80x9d of the water that flows under the collection gallery.
The NC-SBC system may employ a sensor, for alerting to changing hydraulic conditions, the sensor inputting to a control that permits adjustment of the NC-SBC configuration. For example, the NC-SBC may use adjustable connections for affixing the OH-SBC to the upstream side of the barrier.
The NC-SBC may consist of multiple OH-SBC modules that span the entire intake system of a large hydroelectric powerhouse, for example. Each of these modules may be associated with a de-watering screen. The dewatering screen removes water from the collection gallery within the OH-SBC and thereby sets up a slight flow of water through the bottom slot and into the OH-SBC module. Alternatively, water flow into the bottom slot and through the modules may be effected by a manifold such that the water from each module is maintained in a chamber associated with the individual module.
Each NC-SBC system is designed to operate at an optimum level with respect to the intake of the dam or hydroelectric power house at which it is installed, thus customized to overcome a natural hydraulic cue resultant from the operation of that dam or hydroelectric power house""s intakes.
Other design options for a preferred embodiment of the present invention include the reduction of distracting visual cues. For example, to avoid distracting or xe2x80x9cscaringxe2x80x9d the fish the inside of the collector gallery may be painted a neutral color, such as battleship gray. Further, turbulence in the collection gallery may be minimized by providing a smooth surface on its interior surface. Additionally, coating that surface with a material having a low coefficient of friction minimizes turbulence within the collector gallery.
Other options for a preferred embodiment of the present invention include adding stimuli in the region of the collector gallery. This added stimuli may be natural light piped in from the surface, artificial light, sounds proven to be attractive to fish, and combinations thereof. An example of sounds that are attractive to fish is provided in U.S. Pat. No. 4,932,007, Fish Behavior Control System, issued to Suomala, Jun. 5, 1990, and incorporated herein by reference.
Also provided as a preferred embodiment of the present invention is a method for facilitating the migration of fish downstream around a barrier. The method establishes a path in the water near the barrier. The path incorporates the simulation of at least one natural hydraulic cue used by migrating fish, so that they select the path over competing cues and are led to a safe route around the barrier. The simulated natural hydraulic cue capitalizes on an instinctive response of fish to select a portion of a simple, straight stream having a near maximum downstream velocity vector, u, and to minimize at least two strain rate variables in the downstream direction with respect to the depth and the width of the stream, the variables represented mathematically as                     ∂        u                    ∂        z              ⁢          xe2x80x83        ⁢    and    ⁢          xe2x80x83        ⁢                  ∂        u                    ∂        y              ,
respectively. Ideally, both variables approach zero at the point in the profiles having minimum solid boundary effects, which is also the point in the cross section having maximum average downstream water velocity. Minimizing other strain rate variables may be an alternative solution of a preferred embodiment. These other strain rate variables include             ∂      u              ∂      x        ,            ∂      v              ∂      x        ,            ∂      v              ∂      y        ,            ∂      v              ∂      z        ,            ∂      w              ∂      x        ,                    ∂        w                    ∂        y              ⁢          xe2x80x83        ⁢    and    ⁢          xe2x80x83        ⁢                  ∂        w                    ∂        z            
and become important in stream channels that are complex (i.e., that are not approximately u-shaped in cross section) or curved. The method provides for installation of an appropriate number of OH-SBC modules upstream from and adjacent to the barrier, the OH-SBC module""s length oriented parallel to the upstream side of the barrier and its top generally parallel to the surface of the water. The OH-SBC can be any of a number of alternative configurations as described above.
Finally, a barrier can be designed to incorporate the NC-SBC, either as an integral part of an original system or as a modification thereto. These barriers may be any of a number of types commonly used in streams and waterways such as a dam, a hydroelectric powerhouse, a weir, a boom, a sluice gate, a spillway, a berm, and combinations thereof.
A preferred embodiment of the present invention capitalizes on the propensity of outmigrating fish to follow stream lines that minimize turbulence and strain rate in the approach flow field. The design slightly modifies a flow entering into an obstruction in the stream, such as the turbines of a powerhouse, to create a hydraulic gradient in the strain rate hydraulic variables. This gradient is used to guide fish to the entrance of the SBC in a manner that evokes a natural response of the fish.
A preferred embodiment of the present invention is cost effective compared to conventional SBCs because it does not require high flows to be diverted from the artificial barrier, such as a powerhouse, to create an attracting intake plume. Further, large trash racks are not needed since the slot opening only minimally intercepts the flow field. Extensive de-watering facilities, as used with conventional SBCs, are not required since much less water is conveyed into it. Thus, large structures requiring extensive engineering to convey large volumes of flow are not needed. Finally, the deep bottom slot is located in a shaded zone of reduced light intensity. This reduces the migratory fish""s reliance on visual acuity to navigate, resulting in a system that works equally well in changing external lighting conditions.
Further, an alternative configuration may use one or more sensors to detect changing hydraulic conditions and alert to a need to modify physical connections or dimensions. Mechanical adjustments for adjusting to changing hydraulic conditions at the entrance to a preferred embodiment of the present invention also aid in optimizing the simulation of a natural hydraulic cue.